N-, P-, and O-doped porous carbon: A trifunctional metal-free electrocatalyst

Abstract Electrocatalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) are practical mechanisms for sustainable energy conversion and storage. Metal-based electrocatalysts are widely used in the above fields. However, metal-based electrocatalysts have many disadvantages, including resource scarcity, low durability, and damaging environmental effects. To address this dilemma, we investigated a simple pyrolysis mode to synthesize a nitrogen (N), phosphorus (P), and oxygen (O) -doped (i.e., tridoped) defect-rich porous carbon-based electrocatalyst, named as GNP-900, for HER, OER, and ORR by heating the assembled hybrid super molecule of graphene oxide (GO), phytic acid (PA), and polyethyleneimine (PEI) at 900 °C. The developed GNP-900 shows high electrocatalytic activities for HER and OER with low Tafel slopes of 93 mV dec−1 and 127 mV dec−1 and small overpotentials of 179 mV and 299 mV, respectively, to achieve the current density of (j) ± 10 mA cm−2. For ORR, the GNP-900 offers a very small loop current density and presents good CH3OH tolerance. In addition, features with a positive onset potential of 0.96 V and half-wave potential (E1/2) of 0.824 V, strongly suggesting the high electrocatalytic performance. The excellent electrocatalytic performance of the porous GNP-900 is mainly ascribed to the tridoped heteroatoms and the abundant defect sites on the substrate.